OpenCV - can't get any output from camera

Question

I am trying to connect my camera with opencv, but window is showing a grey output screen with no image and output window of vc++ is showing the following error:

... 'opencv practice.exe': Loaded 'C:\Windows\SysWOW64\msyuv.dll', Cannot find or open the PDB file 'opencv practice.exe': Unloaded 'C:\Windows\SysWOW64\msyuv.dll' ...

i tried fining the msyuv.dll, and it is available there.

i have one further question, next to this, i want to implement this on unity3d, so should i stick with opencv or use emgucv?

#include "StdAfx.h"
#include <stdio.h>
#include <stdlib.h>

#include <opencv\cvaux.h>
#include <opencv\highgui.h>
#include <opencv\cxcore.h>

using namespace std;

int main(int argc)
{
    CvCapture* cam = NULL;`
    cvNamedWindow("hi",CV_WINDOW_AUTOSIZE);

    IplImage* img = NULL;
    cam = cvCaptureFromCAM(-1);
    char a;
    while(1)
    {
        if(cam != NULL)
        {
            img = cvQueryFrame(cam);
        }
        else
        {
            printf("erro1");
            return -1;
        }

        cvShowImage("hi", img);
        a = cvWaitKey(20);
        if(a == 27)
            break;



    }

    cvReleaseCapture(&cam);
    cvDestroyAllWindows();
    return 0;
}